Blood vessels within the vasculature of the human body may become diseased due to plaque deposits within the endothelial lining of the vessel wall. Progression of the disease causes narrowing of the vessel segment thus limiting the blood flow across the segment. Ultimately, blood coagulates in the diseased segment causing cellular necrosis in the supply region of the artery, often with fatal results.
A common method of treatment used in restoring normal blood flow through a diseased segment of a blood vessel is balloon angioplasty. As is described in U.S. Pat. No. 4,909,252, the therapy involves the use of a balloon catheter, that is, a balloon fastened around the exterior of a hollow catheter tube. The balloon is placed across the diseased vessel segment and is inflated with sufficient pressure to cause the deposit to compress against the vessel wall.
The above method of intervention, using conventional balloon catheters, causes a complete interruption of blood flow of the vessel while the balloon is pressurized. This blood flow interruption limits the inflation duration of the balloon. Keeping the balloon inflated for an extended period causes a risk of damage to the region nourished by the vessel--a region likely already weakened by insufficient blood supply. Ideally, the situation calls for a device that will compress the deposit against the artery wall for an extended period while maintaining a sufficient flow of blood through the segment. To offset the limitation of the current conventional devices, a repeated cycle of balloon positioning, balloon inflation, balloon deflation, balloon withdrawal from the diseased segment, and fluoroscopic determination of lumen enlargement of the dilated site is performed until sufficient blood flow is restored. This method is tedious, time consuming, cumbersome to the physician and inconvenient to the patient.
As an alternative to a conventional balloon catheter, U.S. Pat. No. 4,909,252 describes a perfusion balloon catheter that allows passage of blood even when the balloon is fully inflated. The cylindrical balloon is substantially donut shaped in cross-section and permits the flow of blood through the blood vessel.
Another type of balloon catheter is described in U.S. Pat. No. 4,762,130. That catheter has a corkscrew-like balloon that can be inflated, reportedly without possible perforation or abrasion of the vessel wall.
A similar device is shown in WO 92/18195, to Shturman et al. The device shown there involves a thin walled, helically coiled balloon suitable for use as an angioplasty catheter. The successive turns of the coil are joined by an adhesive, by longitudinal straps, or by wire.
The current invention involves the use of an inflatable intravascular prosthesis to restore normal blood flow to a diseased vessel. Unlike the balloon catheters described above, the prosthesis is a helically wound polymeric tube, the coil turns preferably secured using longitudinal or helical strips of polymer. The prosthesis is adapted to remain in place inside the blood vessel until normal blood flow resumes and may then be removed. More permanent uses for intravascular stents are known in the art. U.S. Pat. No. 4,820,298 describes the use of an internal vascular prosthesis for clotting and ingrowth of tissue to seal off an aneurysm. The prosthesis is a single helix of thin-walled, elliptical tubing that assumes a natural spiral configuration when released into the vessel. No mention is made of a temporary prosthesis for use in opening a vessel and supporting the vessel wall during angioplasty procedures. Such is also true for copending U.S. patent application Ser. No. 07/011,480 filed 26 Jan. 1993, directed to an endovascular inflatable stent for use in the treatment of aneurysms, diseased blood vessels and other bodily lumen.
In addition to plaque deposits in the blood vessel, restriction of normal blood flow through a segment of the vasculature can be due to other causes. Narrowing of the artery lumen can be caused by vascular spasms. Spasm has been well documented for example, on the segment of an artery proximal in which an aneurysm has been clipped. For this type of clinical case, prolonged dilation of the narrowed segment is highly desirable. A temporary prosthesis that will support the arterial wall and allow sufficient blood flow is a preferred mode of therapy. The temporary prosthesis of the present invention can be kept in place for an extended period of time and be removed once the spasm has subsided.